Parsing JSON with jq

jq is such a useful, powerful tool for parsing the JSON data that many APIs produce.

Albeit perhaps a bit cryptic in syntax (much like regex). But there’s also this fantastic playground at jqplay.org for testing options and producing the command syntax for you.

Selecting fields from an array

My particular need was to get the results of an API call that produces an array of “allowed” values for a data field - Country codes in this case - and convert that into a list of name-value pairs for use elsewhere.

Using this comment in a GitHub Issue as a clear example, with JSON data like the following:

{
    "result": [
        {
            "countryId": "1",
            "countryCode": "AF",
            "countryCode2": "AFG",
            "countryDisplayValue": "Afghanistan",
            "countryDescription": "Afghanistan",
            "active": "True",
            "updatedDate": "1/15/2020 12:45:00 PM"
        },
        {
            "countryId": "2",
            "countryCode": "AX",
            "countryCode2": "ALA",
            "countryDisplayValue": "Aland Islands",
            "countryDescription": "Aland Islands",
            "active": "True",
            "updatedDate": "1/15/2020 12:45:00 PM"
        },
...

We can use this jq filter to merge two fields with an equals sign between them:

.result[] | "\(.countryCode)=\(.countryDisplayValue)"

Or the following jq command:

$ jq --raw-output '.result[] | "\(.countryCode)=\(.countryDisplayValue)"'

Output like:

AF=Afghanistan
AX=Aland Islands